JP6615250B2 - Improved additive manufacturing - Google Patents

Description

  The present invention includes a step of applying a layer of a powder on a base with a coating apparatus, and locally heating the area of the applied layer by a heat treatment using a processing beam to heat the powder particles in the area. In addition, the present invention relates to an operation method of an additive manufacturing (AM) apparatus in which a process of coupling with each other is repeatedly performed.

  The present invention further relates to a computer program for a control device of an additive manufacturing device, wherein the computer program is configured using a machine language (machine code) that can be directly executed by the control device. By executing, the control device operates the additional manufacturing device according to the operation method.

  The invention further relates to a control device for an additive manufacturing device, which is programmed using the computer program described above and operates the additive manufacturing device in operation according to the operating method.

  The present invention further includes a coating apparatus for applying a powder layer on a base, a processing beam generating apparatus for generating a processing beam for locally heating the area of the coating layer, and a detection apparatus for detecting the temperature of the coating layer. And an additive manufacturing apparatus having the control device.

  An operation method as described above, a computer program, a control device, and a manufacturing device corresponding to the operation method are disclosed in, for example, Patent Document 1.

  In Patent Document 1, the coating powder layer is sequentially preheated by another heat treatment before the heat treatment. Preheating seems to be performed over a large area (over the entire coating layer). The heat capacity of the material is determined according to the temperature due to preheating.

  Additive manufacturing often performs layered manufacturing of complex three-dimensional structures. A typical example is so-called SLM (selective laser melting = additive manufacturing method). Other examples include laser sintering, electron beam melting, and electron beam sintering. The quality of the manufactured structure, for example dimensional accuracy, the bonding quality between the individual layers, the cavities and the inclusions are related to a number of parameters.

  A number of manufacturing methods are known in the prior art. However, all of these methods have certain drawbacks.

Published German patent application: DE10236697A1

  The object of the present invention is to provide an improved measure for additive manufacturing (AM).

  The above problem is solved by the operation method of the additive manufacturing apparatus having the features of claim 1. Advantageous aspects of this method of operation are described in the cited forms of claims 2-12.

  According to the present invention, the first heat treatment is performed before the actual heat treatment (hereinafter referred to as the second heat treatment), and the coating layer is applied by the processing beam. The first zone is locally heated so that in this first heat treatment, the powder particles in the first zone are heated but not yet joined together. The first area is defined in correlation with the area heated by the second heat treatment (hereinafter referred to as the second area) (for example, at least partially overlapping with the first area). The temperature profile of the coating layer is detected by the detection device. The temperature profile is evaluated according to the distance from the first zone in the vicinity of the first zone. Alternatively or additionally, the assessment may be performed as a function of time. As part of the evaluation, at least local thermal conductivity or local diffusivity is determined based on the temperature profile for the first zone. The determination is preferably made quantitatively. However, it is also possible to make at least a qualitative determination, i.e., determine whether one or both of the local thermal conductivity and local diffusivity in one region is greater or less than in another region. At least one processing variable of the processing beam involved in heating the second zone is determined as a function of the determined local thermal conductivity or diffusivity for the correlated (at least partially overlapping) first zone.

  In this way, the relationship between the actual heating of the second zone and the target heating can be made better than in the prior art. This improvement in heating improves the bonding between the second area heated by the second heat treatment and the base, and becomes more accurate.

  During the second heat treatment, the coating powder is sintered or melted as usual in the second zone. Further, as usual, the processing beam is a laser or an electron beam. However, other coupling steps and other processing beams can also be envisaged.

  At least one of the first zones can be formed as a linear structure. When performing the spatial evaluation, the temperature profile at this time is preferably evaluated in one dimension orthogonal to the linear structure. Similarly, at least one of the first areas can be formed as a point-like structure. The temperature profile at this time can be evaluated one-dimensionally or two-dimensionally orthogonal to the point-shaped structure when performing spatial evaluation. These treatments can also be combined with each other if one of the plurality of first zones is formed as a linear structure and another as a point structure. In the case of a plurality of point structures, one of the structures can be spatially evaluated in one dimension, and another structure can be spatially evaluated in two dimensions.

  The first zone is preferably correlated to the second zone in an appropriate manner. For example, if the second area is formed as an elongated structure or has a boundary edge, the first area can be formed as a linear structure. The first zone in this case can be parallel or perpendicular to the second zone, or parallel or perpendicular to the boundary edge. If the second zone has corners or overhangs, the first zone preferably contains the corners or overhangs.

  It is also possible to determine the local thickness of the coating layer before the first heat treatment. The “local thickness” as used herein means that determination is made by a spatial decomposition method on the surface of the layer. Appropriate methods are well known to those skilled in the art. The local thickness is considered at least as part of determining at least one processing variable of the processing beam involved in heating the first zone, or as part of determining local thermal conductivity or local diffusivity. Alternatively, in addition to local conductivity or local diffusivity, it can be taken into account as part of determining at least one processing variable of the processing beam involved in heating the second zone.

  Alternatively, the local thickness of the coating layer can be determined after the first heat treatment. In this case, the local thickness determines at least one processing variable of the processing beam involved at least as part of determining the local thermal conductivity or local diffusivity or for heating the second zone. As part, it can be considered in addition to local conductivity or local diffusivity.

  In some cases, it is also possible to perform a target leveling process for leveling variations in local thickness after the determination of the local thickness and before the next heat treatment. For example, the substrate on which the first base is formed in manufacturing the structure to be manufactured can be shaken. Alternatively or additionally, it is also possible to use, for example, a roller device (doctor blade) that distributes the applied powder appropriately.

  Furthermore, it is also possible to detect the local heat capacity and take this heat capacity into account as part of determining at least one processing variable of the processing beam involved in heating the second zone.

As a processing variable of the processing beam, for example, at least one of the following variables can be used:
Output of machining beam;
Feed rate to move the machining beam over the layer;
Modulation of machining beam power;
Processing beam focus variable.

  Preferably, the temperature profile is spectrally filtered before being detected by the detection device so that the machining beam itself is masked in the temperature profile. This optimizes the signal-to-noise ratio.

  It is possible to use a thermographic detection device as the detection device. Alternatively, other detection devices such as a CCD camera can be used.

  The object of the present invention is also solved by a computer program having the features of claim 13. According to the present invention, when the machine language is executed by the control device, the control device operates the additive manufacturing apparatus according to the operation method according to the present invention.

  The object of the present invention is also solved by a control device having the features of claim 14. According to the invention, the control device is programmed by a computer program according to the invention, which activates the additional production device in operation according to the operating method according to the invention.

  The object of the present invention is also solved by an additional manufacturing apparatus having the features of claim 15. According to the present invention, the temperature profile of the coating layer is detected by the detection device. And the control device of the additive manufacturing device is designed according to the present invention.

  The above-mentioned characteristics, features and advantages of the present invention, and modes for achieving them will be clearly and specifically described through embodiments described in detail with reference to the following drawings.

Part of the additive manufacturing apparatus according to the present invention. A part of the additional manufacturing apparatus of FIG. The flowchart which concerns on one Embodiment of this invention. The top view of the layer of powder. One-dimensional temperature profile. Two-dimensional temperature profile. The flowchart which concerns on another embodiment of this invention. The flowchart which concerns on another embodiment of this invention. The flowchart which concerns on another embodiment of this invention.

  1 and 2 show the main part of the additive manufacturing apparatus. Some parts of the additive manufacturing apparatus are shown in FIG. 1 and not shown in FIG. 2, and conversely, there are parts shown in FIG. 2 and not shown in FIG. However, these are not shown whether they are shown only in FIG. 1, only in FIG. 2, or in both FIG. 1 and FIG. Is a component of

  According to FIGS. 1 and 2, the additive manufacturing apparatus includes a coating apparatus 1, a processing beam generation apparatus 2, a detection apparatus 3, and a control apparatus 4. The control device 4 is programmed by a computer program 5. The computer program 5 comprises a machine language 6 that is directly executed by the control device 4. The control device 4 that executes the machine language 6 operates the additive manufacturing device according to the operation method described in detail with reference to FIG. 3 (and other drawings).

  According to FIG. 3, the control device 4 drives the coating device 1 in step S1, whereby the coating device 1 applies the layer 8 of the powder 9 on the ground. The base is the substrate 7 of the additive manufacturing apparatus when the first layer 8 is applied. When the next layer 8 is applied, the base is the coating layer 8 applied immediately before. As an example, FIG. 1 shows the state after applying the powder 9 from the side, with the layer 8 already applied. FIG. 4 shows this state from above.

  In step S <b> 2, the control device 4 defines a first area 10 of the coating layer 8. In particular, the control device 4 defines at least one first area 10 corresponding to each of the second areas 11 of the coating layer 8. The second area 11 of the coating layer 8 is the area of the layer 8 that is to be bonded to the substrate later. The control device 4 correlates the first zone 10 and the second zone 11 and makes the definition, for example so as to at least partially overlap. In order to explain the criteria for defining the first zone 10, a lower case alphabet (af) is appended to each of the first and second zones 10,11.

  In the example where there is a second zone 11a formed as an elongated structure, the corresponding first zone 10a can be formed as a linear structure parallel to the second zone 11a. Alternatively, in the example of the second area 11b formed as an elongated structure, the corresponding first area 10b can be formed as a linear structure orthogonal to the second area 11b. The elongated structures of the second areas 11a and 11b can exist in a curved line in addition to being present as a straight line. However, the linear structure of each first zone 10a, 10b is typically a straight line.

  A similar approach is possible for the second areas 11c, 11d (shown in FIG. 4) with boundary edges. The boundary edge can be a straight line, but does not necessarily have to be a straight line. However, it cannot have a bend (in this case it becomes a corner). Each first zone 10c, 10d is preferably also a linear (in the sense of a straight line) structure.

  In the case of a second zone 11e having a corner, the corresponding first zone 10e should preferably contain that corner. The “corner” is a region where two boundary edges of the second area 11e intersect each other with a predetermined angle. This angle is different from both 0 ° and 180 °. Usually, it can be said to be 45 ° to 135 ° or 225 ° to 315 °. The same is true for the second zone 11f with an overhang (see first zone 10f). The overhang occurs when the second area 11f does not have a fabrication structure in the lower layer 8 (see FIG. 1). In this case, the corresponding first zone 10f should preferably contain an overhang site. Such a lower layer 8 is indicated in FIG. 4 by a broken line with respect to the second zone 11f (only for this region).

  In step S <b> 3, the control device 4 drives the machining beam generator 2, whereby the machining beam generator 2 generates the machining beam 12. The processing beam 12 can be, for example, a laser or an electron beam. The machining beam 12 is directed to the first zone 10 by a deflection device 13 (which can be regarded as a component of the machining beam generator 2). The first zone 10 is thereby heated. However, the machining beam generator 2 at this time is controlled so that the particles of the powder 9 in the first zone 10 are heated by the machining beam 12 by the control device 4, but not yet bonded to each other. Be controlled. Furthermore, only the first zone 10 is heated. Other than the first zone 10 is not heated. That is, the heating in step S <b> 3 is performed locally only in the first area 10 of the coating layer 8.

  After heating the first zone 10, the detection device 3 detects the temperature profile of the coating layer 8. That is, the temperature T generated by the heating in step S3 is detected according to the position in the coating layer 8. As the detection device 3, for example, a thermography detection device can be used. Further, the filter 14 can be disposed in the optical path between the coating layer 8 and the detection device 3. With this filter 14, the temperature profile before being detected by the detection device 3 can be filtered with a spectrum, so that the machining beam 12 itself can be masked in the temperature profile. The detection device 3 can continuously detect the temperature profile. Alternatively, the detection device 3 can detect the temperature profile only in accordance with the control by the control device 4. In any case, the temperature profile is sent to the control device 4, and the control device 4 receives the temperature profile in step S4. In addition, the detection device 3 can detect the temperature profile only in and around the first zone 10. However, the temperature profile can also be detected over the entire coating layer 8. Further, the detection device 3 can detect the temperature profile only once after heating, or can detect the temperature profile several times after heating.

  In step S5, the control device 4 evaluates the detected temperature profile. When the first zone 10 (eg, the first zone 10a) is formed as a linear structure, the temperature profile is evaluated orthogonal to the linear structure. That is, the temperature T is detected and evaluated as a function of the distance x from the corresponding linear structure of the first zone 10. This is illustrated in FIGS. 4 and 5, in which the direction of the distance x is indicated with respect to the first zone 10a, and in FIG. 5, the temperature T is shown as a function of the distance x. That is, the evaluation in this case is performed in one dimension (one dimension). A similar (one-dimensional) evaluation is possible when the first zone 10 (for example the first zone 10e) is formed as a point-like structure (to some extent). This is also shown in FIGS. 4 and 5, from which the direction of the distance x relative to the first zone 10e is known, and in FIG. 5 the temperature T is shown as a function of the distance x. In this case, evaluation in two dimensions is also possible and is illustrated in FIG. FIG. 6 shows a curve (isothermal line) of the same temperature, and the corresponding temperature value is entered. When this two-dimensional evaluation is performed, for example, by evaluating with a circular isotherm, an anisotropic distribution of the thermal conductivity k can be inferred. In the form in which the detection device 3 detects the temperature profile several times after heating, temporal evaluation can also be performed in step S5 (instead of or in addition to the spatial evaluation of heating).

  The evaluation of the temperature profiles for the various first zones 10 can usually be performed independently of each other. This is because only a relatively short distance from each first zone 10 is usually a problem. That is, evaluation of each first zone 10 and its vicinity is sufficient. The heating of the various first zones 10 does not affect each other.

  As part of the evaluation in step S5, the control device 4 determines at least the local thermal conductivity k (unit W / mk) based on the temperature profile of the first zone 10. Preferably, the local thermal conductivity k, ie each numerical value, is determined quantitatively. However, in cases where it is sufficient to evaluate the thermal conductivity k, it is sufficient to qualitatively determine the thermal conductivity k, or it is sufficient to qualitatively evaluate the thermal conductivity k. In other words, in other words, it may be sufficient to determine whether the thermal conductivity k in the predetermined first area 10 is larger or smaller than the other first areas 10.

  In step S <b> 6, the control device 4 determines a machining variable of the machining beam 12 with respect to the second area 11. This determination depends on the local thermal conductivity k determined by the controller 4 in step S5 for the first zone 10 that is correlated (at least partially overlapping) individually for the second zone 11. Done. This processing variable is a processing variable related to heating of the second zone 11.

As the processing variable of the processing beam 12, for example, the output of the processing beam 12 can be used. “Output” in this case does not mean the total output of the machining beam 12 but means the output density (unit W / m ² ) of the machining beam 12 on the coating layer 8. Alternatively or additionally, as a processing variable of the processing beam 12, for example, a feed speed for moving the processing beam 12 on the coating layer 8 can be used. Alternatively or additionally, for example, modulation of the output of the processing beam 12 can also be used as a processing variable of the processing beam 12. That is, it is possible to make a difference as to whether the energy input to the predetermined second area 11 is performed equally, pulsating (pulsed), or at multiple intervals (intermittent). Alternatively or additionally, for example, the focus variable of the machining beam 12 can also be used as the machining variable of the machining beam 12.

  Next, in step S <b> 7, the control device 4 again drives the machining beam generator 2, whereby the machining beam generator 2 generates the machining beam 12. The processing beam 12 is directed to the second area 11 by the deflection device 13. The second zone 11 is thereby heated. The control of the processing beam generator 2 by the control device 4 at this time is different from step S3 so that the particles of the powder 9 in the second zone 11 are heated and combined with each other by the processing beam 12. . For example, in the second heat treatment, the coating powder 9 is sintered or melted in the second area 11. On the other hand, no heating occurs outside the second zone 11. That is, the heating in step S <b> 7 is performed locally in the second area 11 of the coating layer 8.

  In step S8, the control device 4 checks whether or not the manufacturing of the structure to be manufactured is completed. If not completed, the control device 4 drives the actuator 15 in step S9 to lower the substrate 7 by a predetermined amount (in most cases, in the submillimeter range). Thereafter, the control device 4 returns to step S1. That is, steps S1 to S7 are repeatedly executed until the manufacture of the structure to be manufactured is completed.

  FIG. 7 shows a modification of the step of FIG. 7 also includes steps S1 to S5 and steps S7 to S9 in FIG.

In the added step S11, the control device 4 also determines the local heat capacity c (unit J / kgK) of the material made of the powder 9. If necessary, in step S12 prior to step S11, the coating layer 8 can be heated uniformly and over a wide range for the determination in step S11. As with the thermal conductivity k, the determination of the heat capacity c is also preferably made quantitatively and qualitatively in individual cases. Step S6 is replaced with step S13. Step S13 basically corresponds to step S6, but in the case of step S13, the local heat capacity c is additionally considered as part of determining at least one processing variable of the processing beam 12. For example, the control device 4 determines the local diffusion rate D = k / ρc in step S13. ρ is the density (unit kg / m ³ ) of the material consisting of the powder 9.

  The process of FIG. 3 (the same applies to FIG. 7) can be modified as shown in FIG. According to FIG. 8, the controller 4 determines the local thickness d of the coating layer 8 before the first heat treatment in step S21. Further, the control device 4 determines a machining variable of the machining beam 12 in step S22. The processing variable of the processing beam 12 determined in step S22 affects the heating of the first zone 10. Therefore, the execution of step S3 is affected by step S22. Alternatively or additionally, step S5 can be replaced by step S23. Step S23 basically corresponds to step S5. However, the determined local thickness d is additionally considered as part of the evaluation of the temperature profile (that is, determination of the local thermal conductivity k or the local diffusivity D). Alternatively or additionally, step S6 can be replaced by step S24. Step S24 basically corresponds to step S6. However, the local thickness d is additionally taken into account as part of determining the processing variables of the processing beam 12. That is, the processing variable of the processing beam 12 is determined not only in relation to the local thermal conductivity k or the local diffusivity D but also in relation to the local thickness d. Further, the leveling process can be executed in step S25. The leveling process has the purpose of leveling variations in the local thickness d. Step S25 is always executed after step S21 and before the first heat treatment, that is, before step S3, when employed in the embodiment of FIG.

  A modification of FIG. 9 is possible instead of the modification of FIG. The process of FIG. 9 is similar to the process of FIG. However, in the case of FIG. 9, step S21 is not performed before the first heat treatment (step S3) but after the first heat treatment (and before the second heat treatment). In this case, step S22 is omitted. However, in this case as well, the local thickness d is considered as part of step S23 (ie as part of the evaluation of the temperature profile, the determination of the local thermal conductivity k or the local diffusivity D), or In addition to this, it can be considered as part of step S24 (ie as part of determining the processing variables of the processing beam 12 according to the local thermal conductivity k or the local diffusivity D). Step S25 can continue to be employed. However, in the case of the embodiment according to FIG. 9, it is executed before the second heat treatment, not before the first heat treatment.

  In summary, the present invention has the following features.

  A layer 8 of powder 9 is applied on the substrate. The processing beam 12 locally heats the first area 10 of the coating layer 8 so that the particles of the powder 9 in the first area 10 are heated but not yet bonded together. The temperature profile of the coating layer 8 is detected. This temperature profile is evaluated in the vicinity of the first zone 10 as a function of either or both the distance x from the first zone 10 and the time. As part of the evaluation, at least the local thermal conductivity k or the local diffusivity D is determined quantitatively or qualitatively based on the temperature profile for the first zone 10. Then, for the second area 11 of the coating layer 8 that correlates with the first area 10 (the second area 11 that at least partially overlaps the first area 10), the processing beam 12 causes the second area 11. Heating locally so that the particles of powder 9 inside are bonded together. At least one processing variable of the processing beam 12 involved in the heating of the second zone 11 is related to the determined local thermal conductivity k or diffusivity D for the correlated first zone 10 (at least partially overlapping). Decide accordingly.

  The present invention has many advantages. In particular, local variations in either or both of thermal conductivity k and diffusivity D can be considered in a simple manner. This is particularly important when the material comprising the powder 9 is a metal. This is because metals (unlike synthetic resins) have a thermal conductivity k in the range of 100 W / mK and often higher.

  Although the invention has been illustrated and described in detail with advantageous embodiments, the invention is not limited to the disclosed embodiments. Those skilled in the art can derive various other application forms without departing from the protection scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Application | coating apparatus 2 Processing beam generator 3 Detection apparatus 4 Control apparatus 5 Computer program 6 Machine language 7 Substrate 8 Layer (coating layer)
9 Powder 10 First zone 11 Second zone 12 Processing beam 13 Deflector 14 Filter 15 Actuator

Claims (15)

An operation method of an additional manufacturing apparatus,
A step of applying a layer (8) of powder (9) on a base by means of a coating device (1);
In the first heat treatment by the processing beam (12), the particles of the powder (9) in the first area (10) of the coating layer (8) are heated in the first area (10). But locally heating so that they still do not bond to each other,
Detecting a temperature profile of the coating layer (8) by the detection device (3);
Evaluating the temperature profile in the vicinity of the first zone (10) as a function of either or both of the distance (x) and time from the first zone (10);
As part of the evaluation, quantitatively or qualitatively determining at least local thermal conductivity (k) or local diffusivity (D) based on a temperature profile of the first zone (10);
In the second heat treatment by the processing beam (12), a second area (11) of the coating layer (8) that correlates with the first area (10) is included in the second area (11). At least one of the processing beams (12) involved in the heating of the second zone (11), such that the particles of the powder (9) in are heated and bonded together Determining the two processing variables as a function of the determined local thermal conductivity (k) or diffusivity (D) with respect to the correlated first zone (10). Method.   The operating method according to claim 1, wherein the powder (9) is sintered or melted in the second heat treatment for the second zone (11).   The operating method according to claim 1 or 2, wherein the processing beam (12) is a laser or an electron beam. At least one said first zone (10) is formed as a linear structure;
The operation method according to claim 1, wherein the temperature profile is evaluated in a one-dimensional manner orthogonal to the linear structure. At least one said first zone (10) is formed as a point-like structure;
The operating method according to any one of claims 1 to 4, wherein the temperature profile is evaluated in one or two dimensions orthogonal to the point-like structure. If the second zone (11) is formed as an elongated structure or has a border edge, the correlated first zone (10) is parallel to the second zone (11). Formed as a linear structure that is orthogonal or orthogonal, or parallel or orthogonal to the boundary edge,
6. If the second zone (11) has corners or overhangs, the first zone (10) correlating with it contains the corners or overhangs. Driving method described in 1. Prior to the first heat treatment, the local thickness (d) of the coating layer (8) is determined, and the local thickness (d) is used at least for heating the first zone (10). As part of determining the processing variables of the processing beam (12) involved, or as part of determining the local thermal conductivity (k) or local diffusivity (D), or the second zone ( 11) in addition to the local thermal conductivity (k) or local diffusivity (D) as part of determining at least one processing variable of the processing beam (12) involved in the heating of After the heat treatment of 1, the local thickness (d) of the coating layer (8) is determined, and the local thickness (d) is determined based on at least the local thermal conductivity (k) or the local diffusivity. As part of determining (D) or the processing zone relating to the second zone (11) heating. 7. In addition to the local thermal conductivity (k) or the local diffusivity (D) as a part of determining at least one processing variable of the program (12) The operation method according to claim 1.   The leveling process is performed according to claim 7 for the purpose of leveling variations in the local thickness (d) after the determination of the local thickness (d) and before the next heat treatment. how to drive.   Determining also the local heat capacity (c) and considering the local heat capacity (c) as part of determining at least one processing variable of the processing beam (12) involved in heating the second zone (11); The driving | running method of any one of Claims 1-8.   As the processing variables of the processing beam (12), the output of the processing beam (12), the feed speed at which the processing beam (12) is moved on the coating layer (8), the modulation of the output of the processing beam (12), and 10. The operating method according to claim 1, wherein at least one of the focus variables of the machining beam (12) is used.   11. The machining beam (12) itself is masked within the temperature profile by filtering the temperature profile with a spectrum before detection by the detection device (3). Driving method.   The driving method according to any one of claims 1 to 11, wherein a thermography detection device is used as the detection device (3). A computer program for a control device (4) of an additional manufacturing device,
Composed of machine language (6) executed by the control device (4),
The said control apparatus (4) performs this machine language (6), and the said control apparatus (4) operates the said additional manufacturing apparatus according to the driving | operation method of any one of Claims 1-12. , Computer program. A control device for an additional manufacturing device,
A control device programmed by the computer program (5) according to claim 13 and operating the additive manufacturing device in operation according to the operating method according to any one of claims 1-12. A coating device (1) for applying a layer (8) of powder (9) on the ground;
A machining beam generator (2) for generating a machining beam (12) for locally heating the area (10, 11) of the coating layer (8);
A detection device (3) for detecting a temperature profile of the coating layer (8);
Additive manufacturing apparatus comprising the control device (4) according to claim 14.